1. Field of the Invention
The present invention relates to a lens barrel which houses an image pickup optical system therein, and to an image pickup device which includes the lens barrel.
2. Description of the Related Art
Heretofore, a camera which mounts a zoom lens thereon has been commercially available. The zoom lens is constructed to perform a change of a focal length (zooming) in such a manner that a plurality of lens groups constructing the optical system are moved to desired positions along an optical axis thereof, and to change intervals therebetween.
Meanwhile, a camera which includes a so-called bending optical system in which the optical axis is bent by disposing a reflecting surface, has been known. The camera which includes the bending optical system has an advantage that a lens barrel does not protrude from a front surface of the camera at a time of shooting an image and that a form of the camera is not changed even if performing the zooming.
In order to move such a lens group in the bending optical system, the technique in which a shaft is disposed substantially parallel to the optical axis to use the shaft as a guide shaft for guiding straight the lens group, and a lens frame is directly slid by a motor and a lead screw along the guide shaft to move straight the lens group, is frequently used.
As a lens barrel which houses the bending optical system as described above therein, there is one having a structure in which there is used such a lens barrel split into halves as a barrel member on an object side with respect to an optical axis having been bent by the reflecting surface and as a barrel member on an image surface side with respect thereto, a unit composed of a motor, a lead screw and a holding member thereof for moving one of lens groups is attached onto one of the barrel members, and a unit composed of a motor, a lead screw and a holding member thereof for moving the other lens group is attached onto the other barrel member (for example, refer to FIG. 8 and FIG. 9 in JP-Tokukai-2005-121882A).
Even in the camera including the above-described bending optical system, a request for downsizing and thinning of an outer shape thereof is large. Following this fact, an image pickup optical system built in the camera is required to be further downsized.
The lens barrel described in the foregoing JP-Tokukai-2005-121882A requires spaces necessary for screw holes for attaching, onto the two barrel members, the units each of which is composed of the motor, the lead screw, and the holding member thereof, and further requires spaces necessary for positioning the two barrel members and for screw holes for the purpose of coupling the two barrel members to each other. Since the lens barrel must ensure these spaces, the lens barrel has a drawback that the entirety thereof is upsized undesirably.
Moreover, when the image pickup optical system is shortened, sensitivity thereof to an error of an axial deviation of each lens group is increased. Hence, when each lens group in the lens barrel causes a minute axial deviation in a direction perpendicular to the optical axis, there occurs a problem that image forming performance is decreased.